In the past, various attempts have been made to develop inexpensive light bulbs which do not have the relatively expensive bases of metal or plastic with metal conducting pins or contacts which are found on conventional light bulbs.
One of the more promising light bulbs which has been developed that does not have a base is that disclosed in the Carpenter et al U.S. Pat. No. 3,422,302. The light bulb of that patent includes a filament in a tubular glass envelope and a pair of wire leads connected to the ends of the filament. Each of the wire leads passes through a glass seal at the ends of the envelope to the outside. The portion of the lead which is outside the envelope is bent at a series of angles to form an angular loop and the free end is embedded in the glass seal. Lights having such bent wire loop terminals obviously cannot be used in the conventional socket. Therefore, it has been necessary to develop sockets especially adapted for use with such light bulbs.
One of the most common sockets used for such light bulbs has a pair of shaped leaf spring contacts which are biased away from each other. The bulb is inserted into that socket by hooking the bent wire loop terminals of the bulb over the shaped leaf spring contacts and is retained in the socket by the biased contacts. Although such sockets are fairly widely used they are not without disadvantage. For example, if the outward pressure exerted by the biased lead spring contacts is too great, the embedded end of the bent wire loop can be pulled out of the glass seal damaging the bulb, and if the tension is not great enough the bulb can be dislodged from electrical contact accidentally.